Heretofore in the past, a cluster system, which connects a plurality of servers and operates them as one system, has been used. Each server, which constitutes this cluster system, has been referred to as a node. The cluster system eliminates a node which develops a fault and hands over (transfer) the task which that node performed to another normal node so that the system is allowed to normally operate even though its scale is shrunk and the availability of the entire system is maintained. Further, the cluster system is such that each node has an independent OS, and the software for communication control and status notice among nodes, realization of consistency and monophyty among nodes and, moreover, cluster control for taking over another node task is arranged on the OS and a user application is performed on the OS. Since the cluster system is constituted by the nodes operated by the independent OS in this way, this necessitates a cluster management server which sets definition and operation of resources for each node and monitors a state of each node during the operation. This cluster management server realizes setting, operating and monitoring of the cluster system by a Web browser. The Web browser demands an applet which displays an management screen from the cluster management server which has a function of the Web server and instructs a request which was set and instructed on the applet to each node from the cluster management server. The Web browser can display and monitor a state of each node on the Web browser. For this reason, the cluster system allows any node among the node group to play a role of the cluster management server to perform setting, operating and monitoring of each node. Further, the cluster management server which performs setting, operating and monitoring of each node during the normal operation is taken as a main server and, by way of precaution against incapacitation of the main server to perform the operation due to some cause, the sub-server which takes over a part or the whole of the cluster management task is provided so that the reliability of the cluster system is improved.
By the way, the conventional main server which performs the cluster management task of each server and sub-server which performs a back-up operation thereof are fixedly decided to be the nodes which have a large allowance by taking into consideration a hardware constitution and allotment of applications at the time of the system constitution. However, when both of the main server and the sub-server were incapacitated to perform the operation due to faults and the like, there was a problem that a system manger was unable to use the Web browser and monitor the system and change the constitution, thereby causing interference with the operation of the entire system.